That was new for me to know and I think that it was an incident that can't expect. However, this might be a good issue to study how it happens. This is also a factor that needs to know more properties of the microwave.

If you often cook mixed vegetables from frozen in a microwave, on a microwaveable plate you may notice that carrots produce sparks during cooking and, on closer examination, they display small burns. Why is this? several factors make frozen carrots susceptible to the effect described (although other vegetables also do this).

Firstly, dense vegetables such as carrots have a higher amount of minerals in them - iron, magnesium and selenium - than other food items and sometimes create an arcing effect in a microwave. This tends to happen more in glass dishes. Sparks result as the microwaves reflect or bounce off the metal. the "arcing" does not harm the food, but it does prevent it from heating thoroughly because reflected microwaves will not cook. Also, extensive arcing can damage your oven's magnetron tube. If arcing occurs,turn off the microwave oven and finish cooking the food on the range top.Arcing may occur in other vegetables, and most often appears in green peppers and green beans.

Secondly, while microwaves are extremely good at heating liquid water, ice is almost totally transparent to them, so it is actually quite difficult to get ice to melt in a domestic microwave oven. The "defrost" option on a microwave oven relies on intermittent heating of a small amount of liquid water present on the food, and heat conduction from these areas into frozen material. By putting frozen material into the microwave oven with continuous energy input, no time is given for thermal conductivity effects, and therefore a colossal heating effect occurs on a very localised surface area. These areas, typically at the extreme point of the carrot, will dry out rapidly and then char, essentially forming small carbon points.

Thirdly, carrots are relatively large objects (compared to, say frozen peas) and because microwaves are essentially varying high voltage fields, a large alternating electrical potential exists between the highly conductive charred sections.

Finally, carrots are generally given quite angular cuts, giving sharp points which will yield the highest field gradients. The combination of a large alternating field across a good electrical conductor with sharp points causes electrical breakdown of the air and the sparks which accompany this. Depending upon the precise conditions, it is equally possible for charring to be a secondary effect, rather than a cause. In this case, the discharge may originate from uncharred points, with charring only occurring as a huge current passes through a relatively small point.

Please have You new answers (RESEARCH) about sparking vegetables in Microwave? I have experienced NOT just sparks but IGNITION when i put Chopped dried Celery into microwave; EVEN AT LOW TEMP. AND for 30 seconds..!!! VERY GOOD TOPIC OF RESEARCH..!!! Master´s Thesis or PH D.My background is Earth and Biological Sciences, Master´s in Oceanology, Minor in Aquaculture.. so when i say I´m serious about the question it means: ASTONISHING!!! Seaweed do not SPARK OR BURN(ignite) when put in Microwave...!!!